A polyimide resin is excellent in heat resistance and electric insulation, so that it has various applications, for example, printed wiring board, heat resistant adhesive tape, electrical parts, protective layer for semiconductor devices, and interlayer dielectric film. However, the polyimide resin dissolves in a limited number of organic solvents, causing difficulty in handling in some applications. For easy handling, a polyamic acid, which is a polyimide precursor and more soluble in various kinds of organic solvents than a polyimide resin, is applied on a substrate and then heated at a high temperature for a long period of time to be imidized by dehydration and cyclization into a polyimide. This imidization of the polyamic acid to a polyimide requires a long time of heating at a high temperature, which tends to degrade the substrate. Insufficient heating, on the other hand, causes a portion of the polyamic acid to remain, which degrades moisture resistance and corrosion resistance of the polyimide.
In place of the polyamic acid, the invention described in Japanese Patent Application Laid-open No. H02-36232 employs an organic-solvent soluble polyimide resin, and a polyimide resin film is made by applying a solution of the organic-solvent soluble polyimide resin on a substrate and heating it to evaporate the solvent. However, the film obtained from the polyimide resin does not have good solvent resistance.
Japanese Patent Applications Laid-open No. H02-147630 and No. H07-268098 describe heat-curable polyimide silicones which have polymerizable side chains and are soluble in an organic solvent. The polyimide silicone described in H02-147630 can be cured either by heat or light. The polyimide silicone described in No. H07-268098 is cured by hydrosilylation of an organohydrogensiloxane. The hydrosilylation, however, takes five hours.